tightening sequence

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naka
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tightening sequence

Postby naka » Thu Jul 01, 2010 9:32 am

Hi I have this question in my portfolio can someone help me with it please.

Describe in detail the tightening sequenceof the main engine bottom end bolts and explain why this sequence is critical ?
Naka

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JK
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Re: tightening sequence

Postby JK » Thu Jul 01, 2010 2:21 pm

welcome to the Forum and a good question to start off with.
Don't panic, I deleted the double post to keep the info in one place.
There is no need to post in more then one area.
Do you have any thoughts on the question..I'm assuming you are a 1st year student somewhere.

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naka
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Re: tightening sequence

Postby naka » Sun Jul 04, 2010 3:59 am

hi jk
i am on tugs as oow engineer ,as all our overhauls are done in drydock by outside contractors i have never be involved ,only thing i can think to do is check makers manual on maintenance when i am back onboard on duty .
Naka

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The Dieselduck
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Re: tightening sequence

Postby The Dieselduck » Tue Jul 06, 2010 9:43 pm

I believe these sequences are to make sure you are not stressing parts. By gradually increasing torque on the bolts, generally in two or three steps, you can be sure that "lop sides" stresses don't develop, and that the bearing shell has the appropriate "crush", at the right places. And that the bolt will remain straight and under uniform stretch.

I can feel a better answer coming from Big Pete, ehehehehe. But its late and I am tired and I see no one else offered up some insight.
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naka
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Re: tightening sequence

Postby naka » Wed Jul 07, 2010 10:11 am

Thanks every little helps
Naka

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JK
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Re: tightening sequence

Postby JK » Thu Jul 08, 2010 3:40 am

From the Alco 251F

Alco Tightening.pdf
ALco Tightening Sequence
(87.92 KiB) Downloaded 386 times



From Deutzs/BV6/8/9M628 Manual

Deutz Big End.pdf
(100.62 KiB) Downloaded 373 times



Tightening Torques:

Deutz 3.5.pdf
(59.1 KiB) Downloaded 381 times


Tightening Procedure

Deutz Tightening.pdf
(71.86 KiB) Downloaded 357 times



Followed by hernia, hospital stay, surgery and 6 weeks recovery.

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naka
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Re: tightening sequence

Postby naka » Sat Jul 10, 2010 11:07 am

cheers for the help
Naka

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Big Pete
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Re: tightening sequence

Postby Big Pete » Thu Jul 15, 2010 3:10 am

Hi and welcome to the site,
I think JK's links pretty well cover it.
I would emphasise that as you tighten up you should always keep checking that the BE is still floating freely fore and aft on the crankshaft. I had a Polish 3/E overhauling a generator unit a few years ago, before he started you could bar the engine over with one hand, I came back from the cargo pump room and he and the fitter had got the head on and both of them were jumping up and down with their feet off the deck, and both hands on the turning bar trying to turn the engine!!!! (so that they couls set the valve clearances)
The engine was moving mm by mm and squeaking as it went. It took me half an hour to persuade them that there was something wrong, they kept insisting that now everything was good because they had fitted new bearings. When I eventually got them to strip down the unit we found a big lump of the old bearing metal adhering to the crankshaft, the new bearing shells had clamped on to it like a brake.
BP
It is always better to ask a stupid question than to do a stupid thing.

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Sébastien
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Re: tightening sequence

Postby Sébastien » Fri Jul 16, 2010 8:37 am

I had an identical occurrence to the one that Big Pete mentioned except not so obvious to figure out. Turns out that on this older model generator engine all bearing sets have the same part number, even if they are undersized. A new undersized bearing was fitted by mistake, whenver the big end bolts were loose the engine would bar over no problem but when the bolts were torqued down it would jam tight. To make matters worse, taking the bearing out for inspection showed no abnormalities and the Babbitt metal seemed fine, re-install the bearing and try again same problem. After three tries measured the new bearings and compared with the old ones, the bearing was smaller in diameter by just about the amount of clearance that should be present.


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